The weather agency said the heat and humidity could lend intensity to a system of slow-moving storms expected to move through the region, resulting in "torrential downpours".

Very strong wind gusts can damage buildings, down trees and blow large vehicles off the road. The overnight low will drop to 15 C. Take cover immediately, if threatening weather approaches.

Environment Canada said a cool down is expected on Friday with the passing of a cold front.

Earlier on Thursday Environment Canada forcasted a daytime high of 34 C today, though humidex values will make it feel as hot as 43 at times.

Environment Canada is forecasting a high of 25 C on Friday with an overnight low of 10 C heading into Saturday.

The temperature is now 31°C in Toronto, with a humidex reaching 43°C this afternoon.

Sunday looks like a high of 26 C with a mix of sun and cloud.

Last week, Environment Canada issued an extreme heat warning for Guelph and the surrounding area, warning that high temperatures would last well into this week, calling it "the most significant heat event in the past few years".